A stent delivery system is a system by which a stent used for improving a stenosis or an occlusion region in a lumen in a living body is inserted into and indwelled at a target region (stenosis or occlusion region). The stent delivery system includes an inflatable balloon disposed on an outer periphery of a distal portion of a hollow shaft portion and a stent disposed on an outer periphery of the balloon and having struts expanded by inflation of the balloon.
Since the balloon includes ridge portions through which the stent is engaged therewith, in a process in which a distal portion of the stent delivery system is inserted into a lumen and is positioned at a target region and then the balloon is inflated to plastically deform the stent so that the stent is closely contacted with and indwelled on an inner surface of the target region, positional displacement and detachment (separation) of the stent from the balloon are suppressed.
The ridge portions of the balloon are formed by inflating, when the stent delivery system is manufactured, the balloon so that part of the balloon projects into spaces between struts and the projected portions are sandwiched by the struts. An example of this is disclosed in U.S. Pat. No. 5,836,965.
However, the ridge portions of the balloon in the conventional technique project from the spaces between the struts to the outside, which increases an outer diameter of the distal portion of the stent delivery system. Therefore, there is a problem that a lumen to which the stent delivery system can be applied is limited.